async function fn() {
    console.log('1')
    // 遇到await的时候会等待直到Promise状态完成并且返回结果
    let two = await Promise.resolve('2');
    console.log(two);
    console.log('3');
    return Promise.resolve('I am here');
};

fn().then(value => {
    console.log(value);
});


// 1 -> 2 -> 3 -> promise